1. Field of the Invention
The present invention relates to a method of storing hydrogen and to a compound including hydrogen and a hydrocarbon and more particularly, to a compound including hydrogen and hydrocarbon having pressure-temperature stability.
2. Discussion of the Related Art
The technology of using hydrogen as an environmentally clean and efficient fuel is an active research area worldwide. Liquid hydrogen, which carries a high density of hydrogen (70 g/liter) and is a commonly used form in prototype automobiles, is very energy intensive; up to 40% of the energy content must be spent to liquefy hydrogen at its very low condensation temperature T of 20° K. This low temperature T cannot be provided by practical and inexpensive cooling agents, e.g., liquid nitrogen (>77° K.); hence, the continuous boil-off of liquid hydrogen poses problems to on-board storage. Compressed hydrogen gas, also a commonly used storage system, typically only holds 15 g/liter at 35 MPa. Higher pressures could hold higher hydrogen densities, but are complicated by safety concerns and logistical obstacles. Other storage methods, including molecular hydrogen adsorption on solids of large surface (e.g., carbon nanotubes) and bonded atomic hydrogen in hydrocarbons or in metal hydrides, have been developed extensively to address key issues of hydrogen content, P-T conditions of synthesis and storage, and on-board hydrogen release.
Storing molecular hydrogen in the host of planetary ices (i.e., major constituents of icy satellites such as H2O, CH4, NH3, CO2, etc.) and other larger molecules as a crystalline molecular compound may provide an attractive alternative method for hydrogen storage. A great variety of gas-ice molecular compounds have been synthesized by varying the P-T conditions and the chemistry of the gases and ices, but systems involving molecular hydrogen have scarcely been studied. Two binaries, H2—H2O (6) and H2—CH4, were previously investigated at high P and 300° K. for their planetary and physical chemistry interest, resulting in the synthesis of a myriad of hydrogen-rich, crystalline compounds. They include H2(H2O)6 (23 g/liter hydrogen), which is stable above 700 MPa; H2(H2O) (110 g/liter hydrogen), which is stable above 2,200 MPa; and H2(CH4)2, H2(CH4), (H2)2(CH4), and (H2)4(CH4), which are stable between 4,500 and 8,000 MPa. These pressures, however, are too high; the hydrogen-bearing solids must be brought to near ambient P to be of practical interest for hydrogen storage. There is still a need for new mixture capable of retaining a significant amount of hydrogen in the moderately low temperature T (20°-300° K.) region. Furthermore, there is a need for methods of storing hydrogen using such compounds.